JP2008112639A - Adhesive for fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an adhesive for a fuel cell capable of hardening certainly regardless of adhering object even if a noble metal system catalyst is contained, and capable of improving reliability of the fuel cell as well as maintaining its performance excellently. <P>SOLUTION: A plurality of unit cells 2 of the fuel cell 1 have an MEA 30 interposed between a pair of separators 20 (20a, 20b) through a frame-like member 40, and the adhesive used for jointing of seal members (13a-13c), the separators 20 (20a, 20b), and the frame-like member 40 contains an adhesive component, a noble metal system catalyst, and a chemical species (including radical, compound) of an atom of iron (Fe), cobalt (Co), nickel (Ni) or the like, or a complex or the like containing these having a higher reactive performance to a curing inhibition substance such as phosphorus (P), nitrogen (N), and sulfur (S) than the catalyst metal. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an adhesive used for a fuel cell.

  In a fuel cell, a fuel gas typified by hydrogen gas and an oxidizing gas typified by air are supplied to the fuel cell, and electric power is generated by a power generation reaction (water generation reaction) between the fuel gas and the oxidizing gas. Various types of fuel cells have been developed. For example, there are no problems such as electrolyte dissipation and retention, solid polymer fuel cells that have advantages such as startup at room temperature and extremely fast startup time. (PEFC: Polymer Electrolyte Fuel Cells) and the like, specifically, a fuel cell stack in which a plurality of fuel cells (single cells) are stacked in order to obtain a high voltage is a moving body such as an automobile. Etc. are being adopted.

The stacking of a plurality of single cells is performed by, for example, a method in which adjacent single cells are partitioned by a separator and stacked and fixed. Usually, for joining of various members and various seals (sealing), A lot of adhesive is used. As this adhesive, an organic adhesive to which a noble metal catalyst such as a platinum catalyst is added is widely used as a component for promoting the curing of the adhesive component. As an example of such an adhesive, Patent Document 1 describes a sealing member using a polysiloxane compound containing a platinum type metal catalyst.
JP-A-2005-507140

  However, according to the inventor's knowledge, when phosphorus (P), nitrogen (N), oxygen (O), sulfur (S), etc. are adhered to the member to which the adhesive is applied, Curing may be suppressed. Such a substance that hinders the curing of the adhesive is caused by, for example, when the adherend is a resin member, it is contained in an antioxidant or a stabilizer added to the resin composition as the material. It is possible. In addition, antioxidants and stabilizers may be added to the adhesive, and the additives include phosphorus (P), nitrogen (N), oxygen (O), sulfur (S), etc. If it has been removed, the curing of the adhesive may be similarly suppressed.

  Therefore, the present invention has been made in view of such circumstances, and “catalysts” such as platinum (Pt) -based catalysts, rhodium (Rh) -based catalysts, palladium (Pd) -based catalysts (hereinafter collectively referred to as “noble metal-based catalysts”). A fuel cell adhesive that can be reliably cured regardless of the adherend, can improve the reliability of the fuel cell, and can maintain its performance at a high level. The purpose is to do.

  In order to solve the above problems, the present inventor has conducted extensive research, and as a result, the noble metal catalyst functions as a “catalyst” that promotes the curing of the adhesive component by being present in an electrochemically unstable state. However, a substance or ion having an unshared electron pair in an atom or molecule such as phosphorus (P) or nitrogen (N), or a relatively small molecular weight of about 500 or less and an unsaturated bond in the molecule. If there are substances (ie, having π electrons) that exist, the catalyst metal such as platinum (Pt) forms a stable bond, the function as a catalyst becomes insufficient, and the adhesive is not sufficiently cured. As a result, the present invention has been reached.

  That is, the fuel cell adhesive according to the present invention is an adhesive used in a fuel cell, and includes an appropriate adhesive component, a Group 9 or Group 10 element, and a second or third transition metal (4d or 5d transition metal), a substance containing an atom of the first element, a catalyst for promoting curing of the adhesive component, a substance having an unshared electron pair in the atom or molecule, or a substance having an unsaturated bond in the molecule And a substance containing an atom of a second element higher in reactivity than the atom of the first element.

  In the fuel cell adhesive having such a structure, it is made of a substance containing an atom of the first element which is a Group 9 or Group 10 element and a second or third transition metal (4d or 5d transition metal). By the noble metal catalyst, curing of the adhesive component is promoted. As one of the components, the noble metal-based catalyst includes reactivity with a substance having an unshared electron pair in an atom or molecule or a substance having an unsaturated bond in the molecule, which is a curing inhibitor of the adhesive component. Since the substance containing the atom of the second element higher than the atom of the first element is also contained, such a curing inhibitor does not react with the noble metal catalyst, and the substance containing the atom of the second element Reacts selectively. In other words, the curing inhibitor is scavenged by the substance containing the atom of the second element. Thereby, even when a curing inhibitor adheres to the adherend, curing of the adhesive is promoted without deactivating the noble metal catalyst.

  Specifically, the substance having an unshared electron pair in an atom or molecule is a group 15 element, in particular, a chemical species (radical, compound) containing an atom of nitrogen (N) or phosphorus (P) or any of them. The same applies hereinafter.) Or a group 16 element, in particular, an oxygen (O), sulfur (S), or selenium (Se) atom, or a chemical species containing any of these, or an intramolecular The substance having an unsaturated bond is alkene, alkyne, aromatic compound, ketone, aldehyde, or imine.

  The second element is preferably a first transition metal element, for example, iron (Fe), cobalt (Co), or nickel (Ni). In this case, the substance containing atoms of the second element is Since it is an atom of the element of the first transition metal or a chemical species including the element, that is, a chemical species such as an atom of iron (Fe), cobalt (Co), nickel (Ni) or a complex including the atom, for example, it is inexpensive. And it is economical.

  According to the fuel cell adhesive of the present invention, the reactivity with the substance having an unshared electron pair in the atom or molecule or the substance having an unsaturated bond in the molecule, which is a curing inhibitor of the adhesive component, is noble metal-based catalyst. The substance containing the atom of the second element higher than the atom of the first element contained in the material functions as a scavenger of the curing inhibitor, and the curing inhibitor does not react with the noble metal catalyst. Even when such a curing inhibitor is adhered, curing of the adhesive is promoted without deactivation of the noble metal catalyst. Therefore, the fuel cell adhesive of the present invention can be reliably cured regardless of the adherend, so that the reliability of the fuel cell can be improved and the performance of the fuel cell can be maintained high. .

  Hereinafter, embodiments of the present invention will be described in detail. In addition, the same code | symbol is attached | subjected to the same element and the overlapping description is abbreviate | omitted. Further, the positional relationship such as up, down, left and right is based on the positional relationship shown in the drawings unless otherwise specified. Furthermore, the dimensional ratios in the drawings are not limited to the illustrated ratios.

  1 to 4 show an example of the structure of a fuel cell using the fuel cell adhesive according to the present invention. This fuel cell 1 includes end plates 8 and 8 provided at both ends in a stacking direction of a stack 3 (fuel cell stack) in which a plurality of single cells 2 (fuel cell) are stacked, and between the end plates 8 and 8. And a tension plate 9 that is applied to the stack 3 and applies a compressive load in the stacking direction to the stack 3 to maintain the state. The fuel cell 1 composed of the stack 3 and the like can be used as an in-vehicle power generation system of a fuel cell vehicle (FCHV), but is not limited to this. It can also be used as a power generation system mounted on a body (for example, a ship or an airplane), a self-propelled device such as a robot, or a power generation system using a stationary fuel cell 1.

  First, FIG. 1 is an exploded perspective view showing a schematic configuration of the single cell 2. The single cell 2 is made of an electrolyte, specifically, an MEA 30 (membrane-electrode assembly), a pair of separators 20 sandwiching the MEA 30 (indicated by reference numerals 20a and 20b in FIG. 1), and the like. It is configured. The MEA 30 and the separators 20a and 20b (fuel cell resin members) are formed in a substantially rectangular plate shape. Further, the MEA 30 is formed so that its outer shape is smaller than the outer shape of each separator 20a, 20b.

  The MEA 30 includes an electrolyte membrane 31 made of an ion exchange membrane made of a polymer material, and a pair of electrodes 32a and 32b (an anode side diffusion electrode 32a and a cathode side diffusion electrode 32b) sandwiching the electrolyte membrane 31 from both sides. . The electrolyte membrane 31 is formed larger than the electrodes 32a and 32b. The electrodes 32a and 32b are joined to the electrolyte membrane 31 by, for example, a hot press method while leaving the peripheral edge portion 33.

  The electrodes 32a and 32b are made of, for example, a porous carbon material carrying a noble metal catalyst such as a platinum alloy or a platinum complex attached to the surface thereof. One electrode 32a is supplied with hydrogen gas as a fuel gas (reactive gas), and the other electrode 32b is supplied with an oxidizing gas (reactive gas) such as air or an oxidant. A chemical reaction occurs and the electromotive force of the single cell 2 is obtained.

  Furthermore, the separator 20 (20a, 20b) is formed of a gas-impermeable conductive material, for example, a hard resin having conductivity, or a metal (metal) such as carbon, aluminum, or stainless steel. Alternatively, a carbon or metal base material whose surface is coated with a conductive hard resin may be used as the separator 20 (20a, 20). Furthermore, a film having excellent corrosion resistance (for example, a film formed by gold plating) may be formed on the surface of the base material on the side of the electrodes 32a and 32b.

  Further, a groove-like flow path constituted by a plurality of concave portions is formed on both surfaces of the separators 20a and 20b. If the separators 20a and 20b are formed of a plate-shaped metal base material (metal separator), these flow paths can be formed by press molding, for example. The groove-shaped flow path formed in this way forms a plurality of hydrogen gas flow paths 35 on the inner surface on the electrode 32a side of the separator 20a, and a cooling water flow on the back surface (outer surface). A plurality of paths 36 are formed. Similarly, a plurality of gas channels 34 for oxidizing gas are formed on the inner surface of the separator 20b on the electrode 32b side, and a plurality of cooling water channels 36 are formed on the back surface (outer surface) thereof.

  Further, the separators 20a and 20b have such a relationship that the concavo-convex shape for forming such a fluid flow path is inverted between the front surface and the back surface. More specifically, in the separator 20a, the back surface of the convex shape (convex rib) forming the hydrogen gas gas flow path 35 is a concave shape (concave groove) forming the cooling water flow path 36, and the gas flow path 35 The back surface of the concave shape (concave groove) forming the convex shape is a convex shape (convex rib) forming the cooling water channel 36. Further, similarly, in the separator 20b, the back surface of the convex shape (convex rib) forming the gas flow path 34 of the oxidizing gas is a concave shape (concave groove) forming the cooling water flow path 36, and the gas flow path 34 is The back surface of the concave shape (concave groove) to be formed is a convex shape (convex rib) that forms the cooling water channel 36.

  Further, at the end of the separators 20a and 20b in the longitudinal direction, an oxidizing gas inlet side manifold 15a, a hydrogen gas outlet side manifold 16b, and a cooling water outlet side manifold 17b are formed. The manifolds 15a, 16b, and 17b are formed by, for example, substantially rectangular or trapezoidal holes provided in the separators 20a and 20b. Further, an oxidant gas outlet side manifold 15b, a hydrogen gas inlet side manifold 16a, and a cooling water inlet side manifold 17a are formed at opposite ends of the separators 20a and 20b. These manifolds 15b, 16a, and 17a are also formed by substantially rectangular or trapezoidal holes, for example. Each of these manifolds is indicated by a symbol in which the suffixes a and b are omitted in FIGS. 3 and 4.

  Among the above-described manifolds, the inlet side manifold 16a and the outlet side manifold 16b for the hydrogen gas in the separator 20a are connected to each other via an inlet side communication passage 61 and an outlet side communication passage 62 formed in the separator 20a in a groove shape. In this way, each communicates with a gas flow path 35 of hydrogen gas. Similarly, the inlet side manifold 15a and the outlet side manifold 15b for the oxidizing gas in the separator 20b are respectively oxidized via an inlet side communication passage 63 and an outlet side communication passage 64 formed in a groove shape in the separator 20b. The gas channel 34 communicates with the gas.

  Further, the inlet side manifold 17a and the outlet side manifold 17b of the cooling water in each separator 20a, 20b are connected to each separator 20a, 20b through an inlet side communication passage 65 and an outlet side communication passage 66 formed in a groove shape. Each communicates with the cooling water passage 36.

  Oxidizing gas, hydrogen gas, and cooling water are supplied to the single cell 2 by the configuration of the separators 20a and 20b as described above. Specifically, when the single cells 2 are stacked, for example, hydrogen gas passes from the inlet side manifold 16a of the separator 20a through the communication passage 61 and flows into the gas flow path 35, and is supplied to the power generation in the MEA 30. , It passes through the communication passage 62 and flows out to the outlet side manifold 16b.

  The seal members 13a and 13b are both composed of a plurality of members (for example, as shown, four small rectangular frames and a large frame for forming a fluid flow path). The seal member 13a is provided between the MEA 30 and the separator 20a, and a part of the seal member 13a is interposed between the peripheral edge 33 of the electrolyte membrane 31 and a portion of the separator 20a around the gas flow path 35. To be provided. The seal member 13b is provided between the MEA 30 and the separator 20b, and a part of the seal member 13b is between the peripheral portion 33 of the electrolyte membrane 31 and a portion of the separator 20b around the gas flow path 34. It is provided so that it may interpose.

  Further, a plurality of members (for example, four small rectangular frames as shown and a large frame for forming a fluid flow path are provided between the separators 20b and 20a of the adjacent single cells 2 and 2. A sealing member 13c formed of a body is provided. This seal member 13c is provided so as to be interposed between a portion around the cooling water flow path 36 in the separator 20b and a portion around the cooling water flow path 36 in the separator 20a, and seals between these. Is. In this embodiment, these sealing members 13a to 13c are formed of an adhesive (adhesive for a fuel cell according to the present invention) that adheres by chemical bonding with an adjacent member. In addition, you may use the elastic body (gasket) which seals a fluid by the physical contact | adherence with an adjacent member as the sealing members 13a-13c. Even in this case, an adhesive (adhesive for a fuel cell according to the present invention) may be used to bond the gasket and the separators 20a and 20b.

  The frame-shaped member 40 is a member (also referred to as a resin frame) made of, for example, resin that is sandwiched between the separators 20a and 20b together with the MEA 30. For example, in this embodiment, a thin frame member 40 made of resin is interposed between the separators 20a and 20b, and at least a part of the MEA 30 such as a portion along the peripheral edge 33 is sandwiched from the front side and the back side by the frame member 40. . In FIG. 1, the frame-like member 40 provided on the separator 20b side is not shown. This frame-shaped member 40 functions as a spacer between the separators 20 (20a, 20b) that supports the fastening force, functions as an insulating member, and functions as a reinforcing member that reinforces the rigidity of the separator 20 (20a, 20b). Have.

  Further, the frame-shaped member 40 and the separator 20 (20a, 20b) are joined by an adhesive (an adhesive for fuel cells according to the present invention). Further, for example, the end portion of the diffusion layer defined in the MEA 30 and the portion holding the electrolyte in the separator 20 (20a, 20b) may be sealed with such an adhesive.

  Here, the adhesive used for various joining as described above is, for example, a reaction between an appropriate adhesive component that becomes an elastomer after curing, a catalyst that promotes curing of the adhesive component, and a curing inhibitor of the adhesive component. And a substance containing an atom of an element having higher properties than the catalytic metal.

  Here, the catalyst is a noble metal catalyst. Specifically, for example, platinum powder, platinum black, chloroplatinic acid, platinum tetrachloride, chloroplatinic acid olefin complex, chloroplatinic acid alcohol solution, chloroplatinic acid and And siloxane complexes. Further, instead of platinum (Pt) as a catalyst metal, it is a Group 9 or Group 10 element such as rhodium (Rd) or palladium (Pd) and a second or third transition metal (4d or 5d transition metal) (second The above-mentioned various compounds containing 1 element atom) can also be used. The amount of the precious metal catalyst used is not particularly limited as long as the adhesive component functions as an adhesive, and also varies depending on the type and composition of the adhesive component used. The amount of the catalyst metal atom is preferably 0.1 to 500 parts by mass. If the amount of the precious metal catalyst used is less than the lower limit, the curing of the adhesive may not be sufficiently accelerated and may be uncured, whereas if the upper limit is exceeded, the cost tends to increase inconveniently. is there.

  Further, the curing inhibitor of the adhesive component is a substance having an unshared electron pair in an atom or molecule, specifically, a group 15 element, particularly an atom of nitrogen (N) or phosphorus (P) or their Chemical species including any of the above, or group 16 elements, particularly oxygen (O), sulfur (S), selenium (Se) atoms or chemical species including any of them, are included in the molecule. Examples of the substance having a saturated bond include alkene, alkyne, aromatic compound, ketone, aldehyde, or imine.

  Furthermore, as a substance containing an element atom (second element atom) having a higher reactivity with the curing inhibitor than the catalytic metal, specifically, for example, an element of the first transition metal, particularly iron ( Chemical species such as complexes containing atoms such as Fe), cobalt (Co), and nickel (Ni) can be preferably used. The amount of this component used is not particularly limited, but is preferably equal to or more than the reaction equivalent amount with the curing inhibitor expected to adhere to the adherend, for example, 0 with respect to the amount of the catalyst metal atom. Examples of the amount of the metal are 1 to 2.0.

  2 and FIG. 3 are perspective views showing a main part of the fuel cell 1 and an overall schematic configuration, respectively, and FIG. 4 is a side view of the fuel cell 1. The fuel cell 1 includes a stack 3 (cell stack) in which a plurality of single cells 2 are stacked, and current collector plates 6 and 6 with output terminals 5 are provided outside the single cells 2 and 2 located at both ends of the stack 3. The insulating plates 7 and 7 and the end plates 8 and 8 are arranged in this order.

  The stack 3 is constrained in a stacked state by a tension plate 9. The tension plate 9 is provided so as to bridge between both end plates 8, 8. For example, the tension plate 9 is disposed so that a pair faces both sides of the stack 3. The tension plate 9 is connected to the end plates 8 and 8 and maintains a state in which a predetermined fastening force (compression load) is applied in the stacking direction of the single cells 2. Further, an insulating film (not shown) is formed on the inner side surface (the surface facing the stack 3) of the tension plate 9 in order to prevent electric leakage and sparks.

  In addition, as a member (elastic module) for applying a fastening force (compression load) to the stack 3, an elastic body 11 such as a coil spring arranged in parallel with each other and the plurality of elastic bodies 11 are sandwiched in the stacking direction. A pair of plate-like members 12 arranged at one end of the stack 3 can be mentioned. Further, a connecting member 13 is interposed between the plate-like member 12 and the end plate 8, and a structure capable of swinging is realized by a configuration in which the connecting member 13 itself contacts in a flexible or pivot shape. ing. As a result, even if a large number (for example, about 200 to 400) of single cells 2 are stacked and the stack 3 is distorted due to, for example, an equal lateral bias that approximates a trapezoidal shape, the neck is centered on the connection member 13. It is possible to correct the distortion by changing the angle appropriately by the amount corresponding to the bias.

  Further, when the connecting member 13 has a threaded portion, the interval between the plate-like member 12 and the end plate 8 can be changed by the rotation, thereby finely adjusting the overall thickness (overall length) of the stack 3. can do. Thereby, it is easy to finely adjust the fastening force acting on the stack 3. As the connecting member 13 with a threaded portion, a so-called load adjusting screw such as a set screw with a slit can be used.

  In the fuel cell 1 configured as described above, an adhesive including a noble metal catalyst used as the seal members 13a to 13c, an adhesive that joins the frame member 40 and the separator 20 (20a, 20b), and the like. The agent contains an atom of an element having a higher reactivity with a curing inhibitor such as phosphorus (P), nitrogen (N), sulfur (S) than the catalytic metal, for example, a first transition metal element, Since it contains chemical species such as complexes containing atoms such as iron (Fe), cobalt (Co), nickel (Ni), such a curing inhibitor does not react with the catalyst metal of the noble metal catalyst. It reacts selectively with chemical species such as complexes containing atoms such as iron (Fe), cobalt (Co) and nickel (Ni).

  In this way, chemical species such as a complex containing atoms such as iron (Fe), cobalt (Co), nickel (Ni), etc. act as a scavenger for the curing inhibitor, so that the separator 20 (20a, 20b) and the frame Even when such a curing inhibitor adheres to the adherend such as the member 40, the curing of the adhesive is promoted without deactivation of the noble metal catalyst. Thereby, since the adhesive for fuel cells of this invention can be hardened | cured reliably irrespective of a to-be-adhered body, it becomes possible to improve the reliability of the fuel cell 1 and to maintain the performance highly. .

  In addition, atoms of the first transition metal such as iron (Fe), cobalt (Co), nickel (Ni), or other chemical species such as a complex containing the same or chemical species containing the element are inexpensive as a catalyst material. Therefore, it is possible to suppress economic deterioration.

  Furthermore, in the past, attempts have been made to add a large amount of noble metal-based catalyst to the adhesive in advance in order to compensate for poor curing of the adhesive containing the noble metal-based catalyst and promote curing of the adhesive. In addition, the cost is increased due to a large amount of expensive noble metal catalyst. In addition, there is a problem that the shelf life of the adhesive is shortened due to deterioration of the storage stability of the adhesive due to the addition of a large amount of noble metal catalyst. Therefore, although it was tried to make the adhesive into a two-component type using a primer (for example, one component is an adhesive base material and two components are precious metal catalysts), the number of steps is increased in the two-component type. There was also an inconvenience that the process became longer and the economic efficiency was further deteriorated. On the other hand, if the fuel cell adhesive according to the present invention is used, the curing of the adhesive can be sufficiently accelerated without increasing the amount of the noble metal catalyst in the adhesive. And cost reduction can be achieved.

  In addition, this invention is not limited to embodiment mentioned above, A various deformation | transformation is possible in the limit which does not change the summary. For example, the overall structure of the fuel cell 1 is not limited to the illustrated one.

  Since the fuel cell adhesive of the present invention improves the reliability of the fuel cell and can maintain its performance high over a long period of time, the fuel cell is of course mounted on a moving body such as a vehicle or a portable device. Can be widely used in facilities such as commercial and household cogeneration systems (combined heat and power).

2 is an exploded perspective view showing a schematic configuration of a single cell 2. FIG. 1 is a perspective view showing a schematic configuration of a main part of a fuel cell 1. FIG. 1 is a perspective view showing an overall schematic configuration of a fuel cell 1. FIG. 1 is a side view of a fuel cell 1. FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Fuel cell, 2 ... Single cell, 3 ... Stack, 5 ... Output terminal, 6 ... Current collecting plate, 7 ... Insulating plate, 8 ... End plate, 9 ... Tension plate, 11 ... Elastic body, 12 ... Plate-shaped member , 13: connecting member, 13a, 13b, 13c ... sealing member, 15a, 16a, 17a ... inlet side manifold, 15b, 16b, 17b ... outlet side manifold, 20 (20a, 20b) ... separator, 31 ... electrolyte membrane, 32a ... Anode-side diffusion electrode, 32b ... Cathode-side diffusion electrode, 33 ... peripheral part, 34,35 ... gas passage, 36 ... cooling water passage, 40 ... frame-like member, 61,62,63,64,65,66 ... Communication passage.

Claims (3)

An adhesive used in a fuel cell,
An adhesive component;
A catalyst comprising an atom of a first element that is a Group 9 or Group 10 element and a second or third transition metal, and promotes curing of the adhesive component;
A substance containing an atom of a second element that is higher in reactivity with a substance having an unshared electron pair in the atom or molecule or a substance having an unsaturated bond in the molecule than the atom of the first element;
A fuel cell adhesive comprising: The substance having an unshared electron pair in the atom or molecule is a chemical species including an atom of a Group 15 or Group 16 element or any of them,
The substance having an unsaturated bond in the molecule is an alkene, alkyne, aromatic compound, ketone, aldehyde, or imine.
The fuel cell adhesive according to claim 1. The second element is an element of a first transition metal;
The adhesive for fuel cells according to claim 1 or 2.

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